This invention concerns a device for transporting a strand of carrier material that is connected on at least one side to individual chambers spaced apart, following one after another, closed on all sides, containing a quantity of substance and composed of a strip of carrier material.
This type of strand of carrier material provided with chambers is transported especially in the continuous production of infusion bags for making tea. These types of infusion bags consist of at least one chamber that contains a quantity of a substance to be extracted, created by cross-sealing a tube made of filter material and one section of the strip of carrier material connected to the chamber which is used for handling and suspending the infusion bag.
It is either impossible or unsatisfactory to transport a strand of carrier material with chambers, as an intermediate product, especially in the continuous production of infusion bags for making tea, with conventional traction devices, for example tackle blocks, because the chambers made of filter paper material are filled and arranged on the strand of carrier material. The strand of carrier material can only be grasped at discrete places, since otherwise the chambers and/or the quantity of substance in the chambers is damaged. Another problem in the continuous production of infusion bags is with manufacturing tolerances. Thus, the distances between the chambers on the strand of carrier material differ sharply because of manufacturing tolerances which can increase, especially in continuous production, by mutual influence. The reason for these types of manufacturing tolerances is that there are tolerances in the printing of the carrier material, for example different distances between the printing marks on carrier materials with printing marks. This makes it more difficult to transport a strand of carrier material with chambers safely and especially with no damage.
In view of this state of the art, the purpose of the invention is to provide a device for transporting a strand of carrier material with chambers of the type mentioned at the beginning that allows damage-free, reliable, high-speed transport of a strand of carrier material with chambers.
For the technical solution, this invention provides a device of the type mentioned at the beginning, with at least two belts driven independently of one another, a segment of which runs at least partly parallel to the strand of carrier material, and they have cams that are spaced apart on the side facing the strand of carrier material that grasp the strand of carrier material between the chambers and/or in the area where a chamber is connected to the strand of carrier material by interacting with a support and transporting it with the movement of the belts.
In the invention, the strand of carrier material is grasped at discrete places and pulled in the transport direction. The device in the invention has the advantage that transporting a strand of carrier material with chambers is fast and reliable, and the fact that the grasping by the cams is between the chambers and/or in the area where one chamber is connected to the strand of carrier material ensures that the chambers are not damaged. The device in the invention thus permits transport with high production capacity.
The use of two belts driven independently of one another, one segment of which runs at least partly parallel to the strand of carrier material, that have cams spaced apart from one another on the side facing the strand of carrier material also makes it possible, because of the tolerances, especially printing mark tolerances, to equalize differencess in coordinating the division of the chambers on the strand of carrier material. Advantageously, the drives for the belts can be controlled in such a way that the two belts transport the strand of carrier material alternately, and a cam of one belt engages with the strand of carrier material and transports the strand of carrier material, while a cam on the other belt is put in a position to grasp the strand of carrier material and then transports the strand of carrier material. This allows the strand of carrier material to be transported in a position that is absolutely precise. Servo motors are advantageously used to drive the belts.
In another advantageous embodiment of the invention, the drives are controlled by printing marks, and the printing marks are preferably arranged on the strand of carrier material. Optical sensors are provided to control the drives on the transport device in the invention, and they detect the printing marks placed on the strand of carrier material and drive the belts in such a way that the cams can be brought into position to grasp the strand of carrier material.
In another advantageous embodiment of the invention, the belts of the transport device are arranged next to one another in the direction in which the strand of carrier material is transported, and the segments of the belts running at least partly parallel to the strand of carrier material at least partly overlap in the direction in which the strand of carrier material is transported. The belt areas therefore run perpendicular to the transport direction one after the other in the direction in which the strand of carrier material is transported.
Another very advantageous embodiment of the invention has two independently driven belts on both sides of the strand of carrier material that are opposite one another, at least in the area where the segment runs parallel to the strand of carrier material. Advantageously, the belts opposite one another are driven by a drive, and the cams of the opposite belts are purposely aligned in such a way that they form a mutual support, so the cams opposite one another on the opposite belts practically form tongs for grasping the strand of carrier material.
In another advantageous proposal, the cams are spring-mounted, at least on one side of the belts, to guarantee an absolutely secure hold and simultaneously rule out any damage to the strand of carrier material or the chambers. In one specific embodiment of the invention, the belts each run over a drive wheel, an output wheel and a tension wheel, which are arranged in the form of a triangle in relation to one another, and the segment parallel to the strand of carrier material runs between the drive wheel and the deflection wheel and is opposite the tension wheel. Because of the triangular arrangement of the drive wheel, the output wheel and the tension wheel, the transport device in the invention can be built extremely compactly. In one advantageous embodiment of the invention, the cams are distributed at spots on the belts in such a way that the strand of carrier material can be grasped in the area near the space or connection between every two chambers, or especially preferred every fourth chamber.